Conventional labels are generally pressure-sensitive and usually consist of paper or plastic shapes created from sheets and spaced apart on a web by die cutting, and matrix or skeleton-stripping of the interstitial waste areas. The web (linear or carrier) typically has a release layer applied to one side and the adhesive and face (label) layer are applied to this release layer, adhesive first. The labels are identified by stripping away the skeleton of the waste face and adhesive, which also allows correct dispensing of the labels.
The facestock of such labels usually carries graphics or indicia on the exposed surface of the applied label, and may be subject to such as oxidation, scuffing and adhesion failure.
The above labels are most often referred to as "laid-on labels", and are made by die-cutting, for example as described in U.S. Pat. No's 2,391,539 and 3,166,186. These disclose a method wherein a sheet or roll of laminated construction (a layer of label facestock, a layer of pressure-sensitive adhesive and a temporary carrier web having a release surface in contact with the adhesive) provides discrete labels by die-cutting through the label facestock and adhesive layer, without cutting through the carrier web, to define the periphery of the individual labels. The facestock and adhesive surrounding the individual labels forms a continuous, skeletal web or matric which is stripped from the carrier web to leave discrete, spaced apart labels adhering to the carrier web. Printing and protective coatings are applied to any suitable stage. The precision required for cutting means that any error is likely to result in either cutting through the web or leaving the skeleton still partially attached to the labels.
Laid-on labels having an adhesive layer in contact with the release surface of a carrier web are typically dispensed in one of two ways. An individual label may be manually peeled from the carrier sheet and applied to a substrate, or the carrier web may be bent over a sharp angle, for example, by drawing the carrier across an edge, and the less flexible label becomes at least partially separated from the carrier web. The separated portion of the label may then be applied directly to a substrate or grasped manually for removal from the carrier web.
In both of the above methods of label dispensing, it is necessary that the label itself possess sufficient rigidiity and strength to survive removal from the carrier film and the transfer to a substrate. In addition, a label manually removed from the carrier web must have sufficient thickness to be readily grasped by the user.
The practice of making laid on labels by die-cutting and stripping of the matrix is wasteful of materials and requires the use and maintenance of precision die-cutting machinery.
It is possible to apply laid-on-labels to inset surfaces, but considerable error can accrue when transferring the labels from web to substrate. Two contructs attempting to avoid these problems are described in U.S. Pat. No's 4,022,926 to Keough, et al, and 4,219,596 to Takemoto et al.
Keough describes a method of printing a liquid, pressure-sensitive adhesive in the predetermined pattern of the label areas directly onto the release surface of a carrier web, leaving areas of the web uncoated by adhesive. The adhesive is solidified, and a face film of radiation-polymerisable liquid is formed over each adhesive area and solidified.
Takemoto provides a label construct comprising a temporary carrier web having a release surface with a label releasably adhered, face down, to the release surface. The labels comprise individual areas of radiation cured face film in contact with the release suface of the carrier web, with a layer of pressure-sensitive adhesive away from the carrier web. Indicia may be located between the face film and the adhesive. A backing protects the adhesive and has a release surface in contact with the adhesive, adhesion between the two being necessarily weaker than adhesion between the release surface of the temporary carrier web and the face film. The protective backing can thus be removed from the label to expose the adhesive while leaving the label releasably adhered to the carrier web. The exposed adhesive of the label is applied to a substrate and the temporary carrier web removed, leaving the label adhered to the substrate.
The above systems offer discrete label shapes but are not ideal, as accurate application relies upon the label shapes remaining in register even under tight winding of the carrier web, necessary to avoid telescoping. Both systems are subjected to predispensing of labels, or movements of labels relative to one another, which results in the loss of ability to locate labels with precision. Winding of the carrier web can also easily result in loss of register.